1. Technical Field
The present invention relates to methods for manufacturing piezoelectric thin film resonators, piezoelectric thin film resonators, frequency filters, methods for manufacturing oscillators, oscillators, electronic circuits, and electronic apparatuses.
2. Related Art
For communications at higher speeds and in greater capacities, electronic components, such as, resonators, oscillators, filters and the like that can be used at higher frequencies and in broader bands are desired. Resonators, oscillators and filters which use surface acoustic wave (SAW) are known as such electronic components. However, in SAW devices, the electrode width of comb-teeth electrodes needs to be miniaturized, such that problems may arise in the manufacturer of thin lines, dielectric breakdown strength of electrodes and the like. In this respect, piezoelectric thin film resonators that use piezoelectric thin films are attracting attention.
Piezoelectric thin film resonators may readily be made for operations at a high frequency because their frequency can be controlled by the film thickness of piezoelectric thin films and therefore their electrodes do not need to be formed into minute patterns. Because their electrodes do not have to be miniaturized, the electrodes have greater dielectric breakdown strength. Also, although piezoelectric thin film resonators use bulk acoustic waves, they generally have an electromagnetic coupling coefficient greater than that of SAW devices using surface acoustic waves, such that they are advantageous in broadening the band.
It is an object of the present invention to provide a method for manufacturing piezoelectric thin film resonators having excellent characteristics, and piezoelectric thin film resonators obtained by the manufacturing method. Also, it is another object of the present invention to provide frequency filters having the piezoelectric thin film resonators. Further, it is another object of the present invention to provide a method for manufacturing oscillators having excellent characteristics, and oscillators obtained by the manufacturing method. Also, it is another object of the present invention to provide electronic circuits having at least one of the frequency filter and the oscillator, and electronic apparatuses having the electronic circuit.